Butadiene telomerization catalyst and preparation thereof

ABSTRACT

Catalyst compositions are prepared by contacting a palladium source and 1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane and a methoxyocta-diene compound, in a primary aliphatic alcohol, under suitable conditions including a ratio of equivalents of palladium to equivalents of 1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane ranging from greater than 1:1 to 1:1.3. The result is a complex of palladium, a 1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaada-mantane ligand, and a ligand selected from a methoxyoctadiene ligand, an octadienyl ligand, or a protonated octadienyl. Such complexes may, in solution, exhibit surprising solubility and storage stability and are useful in the telomerization of butadiene, which is a step in the production of 1-octene.

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 62/145,650, filed on Apr. 10, 2015, entitled “ButadieneTelomeriztion Catalyst and Preparation Thereof,” which is incorporatedherein by reference in its entirety as if copied herein.

This invention relates generally to preparation of a butadienetelomerization catalyst precursor.

Because octane has important and commercially valuable uses in thegasoline fuel industry, improved processes to produce its convenientstarting material, 1-octene, have long been sought. One of the steps inproducing 1-octene is the telomerization of butadiene. Examples ofprocesses to telomerize butadiene include that disclosed in U.S. Pat.No. 8,558,030, which is a process that includes contacting butadiene andan organic hydroxyl compound represented by the formula ROH, where R isa substituted or unsubstituted C₁-C₂₀ hydrocarbyl and the organichydroxyl compound is not glycerol, in a reaction fluid in the presenceof a palladium catalyst and a phosphine ligand represented by formulaPAr₃, wherein each Ar is independently a substituted or unsubstitutedaryl having a hydrogen atom on at least one ortho position, and at leasttwo Ar groups are ortho-hydrocarboxyl substituted aryls. The phosphineligand has a total of 2, 3, 4, 5 or 6 substituted or unsubstitutedC₁-C₂₀ hydrocarboxyls and, optionally, two adjacent substituents on anAr group can be bonded to form a 5- to 7-membered ring.

A typical process for preparing a catalyst precursor used intelomerization of butadiene to produce 1-octene involves batchwisedissolution of one equivalent of palladium acetyl acetonate([Pd(acac)₂]) and two equivalents of a triarylphosphine (PAr₃) (e.g.,triphenyl phosphine (TPP) or tris(5-chloro-2-methoxyphenyl)phosphine(TCMPP) in methanol. This precursor is stabilized by acetic acid that isalso added during pre-catalyst solution make-up, resulting in a saltthat is soluble in methanol and in a +2 oxidation state. Undertelomerization reaction conditions, the palladium (Pd)(II)-containingcatalyst precursor appears to be reduced by a sodium methoxide promoterin methanol in the presence of 1,3-butadiene to a palladium(Pd(0))bis-phosphine complex designated as [Pd(PPh₃)₂]. Subsequent addition of1,3-butadiene results in formation of a (PPh₃)_(1 or 2)-Pd-(octadienyl)complex. Further reaction with methanol leads to formation of either1-methoxy-2,7-octadiene (MOD-1) or 3-methoxy-1,7-octadiene (MOD-3). Atlow temperatures such as those within a range of from 25 degrees Celsius(° C.) to 60° C., the reaction may include an induction period due toreduction of the Pd(II) species to an active Pd(0) complex. Thisreduction may occur more slowly than the telomerization reaction, andtherefore the induction period may occur before the telomerizationreaction can attain its maximum rate. Those skilled in the art thereforemay desire to reduce, preferably substantially reduce, and morepreferably eliminate, this induction period.

Hausoul, et al., in “Facile Access to Key Reactive Intermediates in thePd/PR₃—Calalyzed Telomerization of 1,3-Butadiene,” Angew. Chem. Int. Ed.2010, 49, 7971-7975, notes that Pd-catalyzed telomerization of1,3-dienes is an important atom-efficient transformation that providesan economically attractive route to production of C₈ bulk chemicals suchas 1-octanol and 1-octene. Hausoul reports on preparation of catalystcomplexes that include phosphine ligands such as PPh₃(triphenylphosphine), TOMPP (tris(2-methoxyphenyl)phosphine) and TPPTS(3,3′,3″-phosphinidynetris(benzenesulfonic acid) trisodium salt). Thepreparation uses a solvent mixture such as a 1:1 volume mixture ofdichloromethane and methanol.

Benn, et al., in “Intermediates in the Palladium-Catalyzed Reactions of1,3-Dienes. 2. Preparation and Structure of(η¹,η³-Octadiendiyl)palladium Complexes,” Organometallics 1985, 4,1945-1953, reports preparation of a series of(η¹,η³-octadiendiyl)palladium complexes, [Pd(L)(η¹,η³-C₈H₁₂)] and [Pd(L)η¹,η³-Me₂C₈H₁₀)], by reacting bis(η³-2-methylallyl) palladium with donorligands and butadiene or isoprene, and tetrahydrofuran (THF) as asolvent.

Behr, et al., in “Octadienyl-Bridged Bimetallic Complexes of Palladiumas Intermediates in Telomerization Reactions of Butadiene,”Organometallics 1986, 5, 514-518, discusses preparation of the titlecompounds using a solvent such as methanol, THF or benzene.

Hausoul, et al., in “Mechanistic Study of the Pd/TOMPP-CatalyzedTelomerization of 1,3-Butadiene with Biomass-Based Alcohols: On theReversibility of Phosphine Alkylation,” ChemCatChem 2011, 3, 845-852,discloses testing of several catalyst systems, with emphasis uponPd/TOMPP (tris(2-methoxyphenyl)phosphine).

Vollmüller, et al., in “Palladium-Catalyzed Reactions for the Synthesisof Fine Chemicals, 16, Highly Efficient Palladium-CatalyzedTelomerization of Butadiene with Methanol,” Adv. Synth. Catal. 2001,343, 1, 29-33, details use of methanol under argon to prepare a catalystprecursor from triphenylphosphine and palladium(II) acetate.

Jackstell, et al., in “An Industrially Viable Catalyst System forPalladium-Catalyzed Telomerizations of 1,3-Butadiene with Alcohols,”Chem. Eur. J. 2004, 10, 3891-3900, describes use of methanol inpreparation of catalyst precursors.

Vollmüller, et al., in “Palladium-Catalyzed Reactions for the Synthesisof Fine Chemicals, 14, Control of Chemo- and Regioselectivity in thePalladium-Catalyzed Telomerization of Butadiene with Methanol,”Catalysis and Mechanism 2000, 8, 1825-1832, usesmono(phosphane)-palladium(0)-diallyl ether complexes,Ar₃P-Pd(CH₂═CHCH₂)₂O, as catalysts to dimerize 1,3-diene, specificallybutadiene, in the presence of a nucleophile, in this case methanol.MOD-1 is a primary product, but MOD-3 and other materials are present asbyproducts. Vollmüller, et al., state that the catalyst does not need tobe activated (e.g., by ligand dissociation, reduction, etc.) beforeentering the catalyst cycle, but does not discuss precatalyst stability.

Hausoul, et al., in “Mechanistic study of the Pd/TOMPP-CatalyzedTelomerization of 1,3-Butadiene: Influence of Aromatic Solvents onBis-Phosphine Complex Formation and Regio Selectivity,” Organometallics,2013, 32, 5047-5057, reports on Pd/TOMPP-catalyzed telomerization of1,3-butadiene with phenols such as p-cresol, guaiacol and creosol.

European Patent Specification (EP) 0 561 779 B1 (Bohley, et al.) relatesto a process for producing 1-octene. The process comprises: (1) reacting1,3-butadiene with a primary aliphatic alcohol (e.g., methanol, ethanol,propanol, butanol, ethylene glycol, propylene glycol and glycerol) oraromatic hydroxyl compound having formula R—OH (e.g., phenol,benzylalcohol, cresols, xylenols, naphtol, and polyhydric compounds suchas resorcinol, hydroquinone, and pyrocatechol, as well as alkyl-,alkoxy- and/or halogen-substituted aromatic compounds such asmethoxyphenol and p-chlorophenol), in the presence of a telomerizationcatalyst comprising palladium and a tertiary phosphorus ligand compound,to form a 1-substituted-2,7-octadiene of formulaCH₂═CH—CH₂—CH₂—CH₂—CH═CH—CH₂—R in which R represents the residue of theprimary aliphatic alcohol or aromatic hydroxy compound; (2) subjectingthe 1-substituted-2,7-octadiene to hydrogenation in the presence of ahydrogenation catalyst to form a 1-substituted octane of formulaCH₃—CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—CH₂—R; and (3) decomposing the 1-substitutedoctane in the presence of a suitable catalyst to form 1-octene. Bothpalladium(II) compounds and palladium(0) complexes may be used as thecatalyst. A catalyst promoter such as an alkali or alkaline earth metalsalt appears to be advantageous. Bohley, et al., teach that any solventthat will solubilize 1,3-butadiene, the active hydrogen-containingcompound, and the catalyst, ligand and optional promoter components maybe used in the process. Suitable inert solvents are a (cyclo)-alkane, anaromatic compound, a polar solvent such as a tertiary alcohol, an amide,a nitrile compound, a ketone, an ester compound, an ether compound,dimethylsulfoxide, sulpholane, and water. While the temperature is notstated to be critical, it ranges from ambient temperature to about 150°C., preferably from about 50° C. to about 100° C., and more preferablyfrom about 70° C. to about 100° C. Pressure is similarly not critical,but is generally between 1 and 40 bars, preferably between 5 and 30bars, and most preferably between 10 and 20 bars.

Co-pending U.S. Patent Application Ser. No. 61/915,781, filed Dec. 13,2013, discloses a process to prepare a telomerization catalyst precursorthat comprises dissolving one equivalent of palladium acetyl acetonateand from 1 to 3 equivalents of a tertiary phosphine ligand, underconditions sufficient to form a catalyst precursor. The tertiaryphosphine ligand may, in one embodiment, be defined by the formulaR1PR2, wherein R1 is an aryl moiety or a substituted aryl moiety or analkyl moiety or a heteroatom-containing alkyl moiety; P is phosphorus;and R2 is independently a heterocyclic oxaadamantyl group.

In one embodiment the invention provides a catalyst composition usefulfor catalyzing the telomerization of butadiene comprising a complexcomprising palladium, a1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantaneligand, and a ligand selected from a methoxyoctadiene ligand, anoctadienyl ligand, and a protonated octadienyl ligand. In certainparticular embodiments the complex is in solution in a primary aliphaticalcohol.

In another embodiment the invention provides a process for preparing acatalyst composition useful for catalyzing the telomerization ofbutadiene comprising dissolving as reagents a palladium source,1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaada-mantane, and amethoxyoctadiene compound in a primary aliphatic alcohol, wherein theratio of equivalents of the palladium to equivalents of the1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantaneranges from greater than 1:1 to 1:1.3, under conditions sufficient toform a catalyst composition comprising a complex of palladium, a1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantaneligand, and a ligand selected from a methoxyoctadiene ligand, anoctadienyl ligand, and a protonated octadienyl ligand, in the primaryaliphatic alcohol.

In yet another embodiment the invention provides a process to telomerizebutadiene comprising contacting butadiene and a catalyst compositioncomprising a complex of palladium, a1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantaneligand, and a ligand selected from a methoxyoctadiene ligand, anoctadienyl ligand, and a protonated octadienyl ligand, under conditionssufficient to telomerize at least a portion of the butadiene.

The present invention provides a catalyst composition; a process toprepare the catalyst composition; and a process using the catalystcomposition; all of which relate in general to accomplishing thetelomerization of butadiene. Such telomerization is an important firststep in the preparation of the commercially valuable chemical 1-octene,which may be, in particular applications, used as an intermediate in thepreparation of a wide variety of other chemicals.

The compositions of the present invention may be prepared by a processcomprising bringing together, at a minimum, the following components:(1) a source of palladium; (2) from greater than 1 to 1.3 equivalents(based upon 1 equivalent of palladium) of1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane;(3) a methoxyoctadiene compound; and (4) a primary aliphatic alcohol. Incertain embodiments, what may be termed an optional fifth component, (5)a promoter, and/or what may be termed an optional sixth component, (6) acarboxylic acid (without reference to the actual order of additionand/or whether both optional components are added), may also be includedin the process to prepare the inventive catalyst compositions.

Selection of the palladium source is preferably made from Pd(II)compounds and Pd(0) compounds. Pd(II) compounds may include, innon-limiting example, palladium acetylacetonate, palladium formate,palladium acetate, palladium propionate, palladium octanoate, palladiumcarbonate, palladium hydroxide, palladium citrate, and combinationsthereof. Of these, palladium acetylacetonate is particularly preferred,as it offers the advantage of relatively low cost, relatively highreactivity, and convenient commercial availability. Pd(0) compounds thatwill lead to active palladium species may also be selected, includingbut not limited to palladium phosphines, palladium alkenes, palladiumdienes, palladium nitriles, and combinations thereof. Examples of thesemay include tetrakis(triphenylphosphine) palladium,bis(1,5-cyclo-octadiene) palladium, bis(dibenzylidene-acetone)palladium, and combinations thereof. Combinations of Pd(II) and Pd(0)compounds may also be selected.

Of particular importance in the present invention is the fact that theprocess includes contacting a specific tertiary phosphine compound,which is1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane,herein denominated as TMPTPA-di-OMe. This oxaphosphaadamantane compoundmay be schematically represented by the two enantiomeric structures,denominated as structures (I) and (II), hereinbelow:

This ligand may be prepared by, for example, the cross-coupling reactionof the secondary phosphine1,3,5,7-tetramethyl-2,4,8-trioxa-6-phosphaadamantane with thecorresponding 2,4-dimethoxyhalobenzene, which may be accomplished via,e.g., a Suzuki coupling. A Suzuki coupling may be carried out bycombining an aryl bromide, such as dimethoxy-bromobenzene, with thesecondary phosphine and a base, such as potassium carbonate, in asolvent, such as a mixture of xylenes. This may be stirred under aninert atmosphere and heated to a temperature of about 110° C., for atime period that enables satisfactory completion of thecarbon-phosphorus cross-coupling reaction. Following this the productthereof may be diluted and purified by column chromatography, orrecrystallized to form a solid. While those skilled in the art willnormally be familiar with this reaction, the reader is referred, forgreater detail, to, e.g., Brenstrum, et al., “Phosphaadamantanes asLigands for Palladium Catalyzed Cross-Coupling Chemistry: LibrarySynthesis, Characterization, and Screening in the Suzuki Coupling ofAlkyl Halides and Tosylates Containing 8-Hydrogens with Boronic Acidsand Alkylboranes,” J. Org. Chem. 2004, 69, 7635-7639, which isincorporated herein by reference in its entirety.

In another embodiment, the desired1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantanecompound may be prepared by the reaction of 2,4-dimethoxyphenylphosphinewith pentanedione. This approach is illustrated in greater detail in,for example, Epstein and Buckler, “A Novel Phosphorus HeterocyclicSystem from the Reactions of Phosphine and Primary Phosphines with2,4-Pentanedione,” J. Am. Chem. Soc. 1961, 83, 3279-3282, which isincorporated herein by reference in its entirety. In one embodiment ofthis procedure the pentanedione may be contacted with hydrochloric acid(HCl) in a pressure bottle, and the bottle then successively evacuated,filled with nitrogen, and filled with 2,4-dimethoxyphenylphosphine.Finally, it is shaken under pressure until a precipitate forms, and theprecipitate is then diluted, filtered, and dried to recrystallize it.The 2,4-dimethoxyphenylphosphine may be prepared by the reaction ofdichloro(2,4-dimethoxyphenyl)phosphine with lithium aluminum hydride.The dichloro(2,4-dimethoxyphenyl)phosphine may, in turn, be prepared bya ZnCl₂-catalyzed Friedel Crafts alkylation of phosphorus trichloridewith 1,3-dimethoxybenzene. While those skilled in the art will be veryfamiliar with the aforesaid preparations, the reader is directed, forfurther detail, to, e.g., Protopopov and Kraft, “Reactions of PhenolEthers with Phosphorus Trichloride II: Reaction of m-Dimethoxybenzenewith Phosphorus Trichloride,” Zhurnal Obshchei Khimii, 1964, 34,1446-1449, which is incorporated herein by reference in its entirety.

Those skilled in the art will be able to discern additional methods andmeans of preparing or otherwise obtaining the 1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane which isrequisite to begin the inventive process as defined herein. It is notedthat both of the above generalized methods for its preparation areassumed to produce racemic mixtures, and such racemic mixtures aredeemed suitable for use in the present invention without furtherprocessing beforehand.

Suitable primary aliphatic alcohols may include, for example, mono- orpolyhydric alcohols, which contain primary OH-groups and which can belinear or branched saturated compounds having up to 20 carbon atoms.Such alcohols may also include unsaturated alcohols, such as allylalcohols. In particular, primary aliphatic alcohols having up to 8carbon atoms, such as methanol, ethanol, propanol, butanol, ethyleneglycol, propylene glycol, glycerol, combinations thereof, and the like,are preferred. More preferably the primary aliphatic alcohol selected ismethanol or ethanol, and most preferably it is methanol.

In carrying out the process of the invention, a methoxyoctadienecompound is included as a starting material. This methoxyoctadiene maybe preferably selected from 1-methoxy-2,7-octadiene,3-methoxy-1,7-octadiene, and combinations thereof. Of these,1-methoxy-2,7-octadiene is more preferred.

As noted hereinabove, in certain embodiments of the invention apromoter, (5), may also be included in preparing the inventive catalystcompositions. The promoter may serve to increase the initial rate ofreaction and/or reduce the induction period when the catalystcomposition is used in catalyzing the telomerization of butadiene. Suchmay be selected from, in non-limiting embodiments, alkoxides, enolates,phenoxides, borohydrides, and hydrazides, all of alkali metals; alkalineearth metals and quaternary ammoniums; alkali metal salts; andcombinations thereof.

Also as noted hereinabove, another component that may be included in theinventive compositions in certain embodiments is a carboxylic acid, (6).The carboxylic acid may be selected from, for example, aliphaticcarboxylic acids having up to about 20 carbon atoms. Such may include,in non-limiting embodiments, formic acid, acetic acid, propionic acid,butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid,pelargonic acid, capric acid, lauric acid, palmitic acid, stearic acid,benzoic acid, and benzylic acid. Preferred are those carboxylic acidshaving from 1 to 6 carbon atoms. Aromatic carboxylic acids such asbenzoic acid and toluene carboxylic acids, and dibasic acids such asadipic acid and the phthalic acids, may also be selected. Finally,combinations of any of the above may also be employed in the inventivecompositions and processes to prepare them.

The proportionality of components requires that, in the inventivecatalyst preparation process, the ratio of equivalents of the palladiumto equivalents of the specified1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane,as added to the primary aliphatic alcohol, range from greater than 1:1to 1:1.3, and preferably from 1:1.2 to 1:1.3. These limits are definedherein with one significant (i.e, decimal) figure, but it will beunderstood that additional significant figures may be inferred,particularly with respect to the phrase “greater than 1:1,” e.g., thismay be read as inclusive of 1:1.11, 1:1.12, 1:1.13, etc. Similarly, thelimit “1:1.3” may be read as inclusive of 1:1.31, 1:1.32, 1:1.33, etc.Within these ranges, the process results in a composition exhibitingsurprisingly enhanced storage stability and solubility in the primaryaliphatic alcohol, which is significantly greater than the sameproperties as exhibited by certain other oxaphosphaadamantaneligand-containing catalysts. It is noted that, when prepared withstarting materials for the complex that are outside of the definedequivalents ratio range (from greater than 1:1 to 1:3), significantstorage stability (i.e., more than 3 days) and/or solubility (i.e.,producing no substantial amount of precipitate, “substantial” beingdefined herein as more than 0.5 weight percent (wt %), based upon totalsolution weight), are surprisingly not obtained. Nonetheless, catalyticeffect in the telomerization of butadiene will usually still beexperienced where catalyst compositions are prepared based upon ratiosof equivalents outside of the greater than 1:1 to 1:1.3 range. It isfurthermore noted that, whether preparation includes equivalents withinor outside of this range, the complex itself will most often present anapproximately 1:1 stoichiometry, of palladium to1,3,5,7-tetramethyl-6-(2,4-dimethoxy-phenyl)-2,4,8-trioxa-6-phosphaadamantaneligand. It is noted further that complex formation in the presentinvention is an equilibrium reaction.

It is further preferred that the overall palladium metal concentrationrange from about 0.02 wt % to about 2 wt %, more preferably from about0.02 wt % to about 1.5 wt %, still more preferably from about 0.1 wt %to about 1 wt %, and most preferably from about 0.25 wt % to about 0.6wt %, based on total solution weight. In preferred embodiments theconcentration of palladium in the solution may range up to about 20,000parts per million by weight (ppmw), although a maximum of about 10,000ppmw is more preferred. The minimum palladium concentration ispreferably at least about 500 ppmw, more preferably at least about 2,500ppmw, and most preferably at least about 3,000 ppmw. It will thereforebe noted that the palladium concentration may preferably range from atleast about 500 ppmw, more preferably at least about 1,500 ppmx, andmost preferably at least about 3,000, to about 20,000 ppmw, morepreferably at least about 10,000 ppmw. These preferred levels take intoaccount the fact that, as the composition, most typically in the form ofa solution of the catalyst complex, enters the telomerization reactor totake part in a butadiene telomerization, it will be diluted as it ismixed with butadiene and, typically, methanol. The goal, therefore, isto use an amount of palladium in forming the complex that is sufficientto ensure that the palladium concentration in the reactor preferablyranges from about 0.1 ppmw, more preferably from about 3 ppmw, and mostpreferably from about 5 ppmw, to about 50 ppmw, and more preferably toabout 25 ppmw. These levels of palladium help to ensure that the overallcatalyst efficiency is acceptable and, in preferred embodiments, withina preferred efficiency range for the commercial scale 1-octeneproduction train in which the catalyst will most desirably be employed.

It is also preferred that the selected methoxyoctadiene compound isadded in an amount ranging from about 0.1 wt % (i.e., approximately 1molar equivalent at 0.1 wt % of palladium) to about 50 wt %, (i.e.,approximately 400 molar equivalents at 0.1 wt % palladium).Proportionately higher amounts of the methoxyoctadiene compound may beemployed where higher concentrations of palladium, e.g., up to about 2wt % palladium, are desired. In each case the weight percent is based ontotal solution weight. The goal is to include in the solution an amountof the methoxyoctadiene compound that is effective such thatsubstantially all, i.e., at least 90 wt %, and more preferably at least95 wt %, of the palladium therein forms a complex with both the1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantaneligand and with the ligand derived from the methoxyoctadiene compound.In order to accomplish this, then, the amount of the methoxyoctadiene ispreferably included in the preparation process in at least an equivalentmolar stoichiometric amount, based upon the amount of palladium.However, a larger amount of the methoxyoctadiene compound will tend toincrease the rate at which the inventive catalyst composition forms.Thus, the methoxyoctadiene compound is preferably added in an amount ofat least 5 wt %, and more preferably from 5 wt % to 25 wt %, based ontotal solution weight. Unlike the palladium to1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantaneequivalents ratio, which is important to ensuring that the inventiveproduct can form a storage stable and solubility-enhanced catalystcomposition, the operable ranges of the palladium/methoxyoctadienecompound ratio are therefore obviously much broader, though rate effectsmay of course be very important in the overall design of a 1-octenetrain.

The optional promoter, (5), where included, is preferably added to thesolution in an amount sufficient to achieve a molar ratio of palladiumto promoter ranging from 1:0.01, more preferably from 1:0.5, up to1:1000, preferably up to 1:800, and more preferably up to 1:600. Mostpreferably the molar ratio of palladium to promoter ranges from 1:2 to1:10.

The carboxylic acid, (6), where included, is preferably added to thecatalyst solution in an amount ranging from 1 to 5 equivalents, basedupon 1 equivalent of the palladium. This carboxylic acid compound may,in some embodiments, serve as the source, or one source, of the protonthat forms the protonated octadienyl ligand. Such proton may also oralternatively be supplied by the primary aliphatic alcohol. Whenemployed, the identity of the counteranion in solution will beindirectly discernible by those skilled in the art via means such ashigh resolution mass spectrometry (HRMS), electrospray-ionization massspectrometry (ESI-MS), and elemental analysis (EA), based upon knowledgeof the existence of the catalyst complex.

The aforesaid components are contacted under conditions sufficient toform an amount of a catalyst composition that comprises palladium and,complexed therewith in solution, two ligands. These ligands are the1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantaneligand, and a ligand derived from the methoxyoctadiene compound. Orderof addition of these components is somewhat interchangeable, although itis generally preferred to contact the palladium (i.e., generally thepalladium source) and the1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantanein solution first, followed by the methoxyocta-diene compound. Where acarboxylic acid is included, such is preferably added thereafter,followed by the promoter, where such is to be also included.

Conditions for this contact may include a temperature ranging from about0° C. to about 100° C., preferably from about 5° C. to about 60° C.Pressure, although not generally considered to be critical, maypreferably range from atmospheric (1.0 standard atmosphere, atm,approximately 101.3 kilopascals (kPa)) or slightly lower (e.g.,prevailing atmosphere is more typically approximately 0.9 atm,approximately 95.0 kPa) to superatmospheric, e.g., to 10.0 atm,approximately 1,013.3 kPa). A pressure near or at atmospheric ispreferred, for reasons of simple convenience. Those skilled in the artwill be able to easily determine and optimize conditions of pressure andtemperature for the inventive process and therefore for preparation ofthe inventive catalyst compositions based upon this information.

Reaction times may desirably range from about 1 hour (h) to about 1000h, preferably from about 2 h to about 100 h, and most preferably fromabout 24 h to about 72 h. As a general rule, with an increase in eitheror both the temperature and the methoxyoctadiene compound concentration,formation of the desired palladium complex in solution, containing thedesired oxaphosphaadamantane ligand and a ligand obtained from themethoxyoctadiene compound, as discussed hereinbelow, becomes more rapid.Those skilled in the art will recognize that either temperature ormethoxyoctadiene compound concentration, or both, may therefore beadjusted to provide a convenient and/or commercially desirable timetherefor. For commercial operation, it is desirable to prepare thedesired composition in an amount of time ranging from about 2 h to about100 h. Reaction times of significantly less than about 100 h may beachieved at temperatures ranging from about 30° C. to about 60° C., withconcentrations of the methoxyoctadiene compound ranging from about 10 wt% to about 50 wt %, based on total solution weight, i.e., from about 75molar equivalents to about 400 molar equivalents, based on palladium at0.1 wt %.

Once the process described hereinabove has been carried out, a complexwill have been formed in solution. This complex comprises palladium, aligand that is1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane,and one of three possible ligands derived from the presence of themethoxyoctadiene compound in solution in the primary aliphatic alcohol.The overall complex may be represented using the general formula[(TMPTA-di-OMe)Pd(Y)], wherein TMPTA-di-OMe is1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane;Pd is palladium; and Y may be, as an end product, an octadienyl ligandor a protonated octadienyl ligand, or Y may be, as an intermediateproduct, a methoxyoctadiene ligand, the exact nature of which willdepend upon the starting selected methoxyoctadiene compound. If thestarting methoxyoctadiene compound is 1-methoxy-2,7-octadiene, then theligand derived therefrom will be 1-methoxy-2,7-octadiene, and where thestarting methoxyoctadiene compound is 3-methoxy-1,7-octadiene, then theligand derived therefrom will be 3-methoxy-1,7-octadiene. With time andunder the above-described process conditions, both of these intermediateligands will transform to form either an octadienyl ligand or aprotonated octadienyl ligand.

It is also noted that, where Y is a ligand selected from one of themethoxyoctadiene ligands or (non-protonated) octadienyl ligand, thecomplex is neutral (uncharged). When Y is a protonated octadienylligand, the complex is cationic (positively charged). Representativestructures for these compositions are shown as (III), (IV), and (V)hereinbelow.

It is therefore to be further understood that, where1-methoxy-2,7-octadiene is selected as the starting methoxyoctadienecompound, the resulting complex composition will have the formula[(TMPTA-di-OMe)Pd(Y)]⁺. The resulting charged composition, which willcontain the protonated octadienyl ligand, is a a pi-allyl olefinspecies. In another embodiment, where 1-methoxy-2,7-octadiene isselected as the methoxyoctadiene compound to start, the complexcomposition will have the formula [(TMPTA-di-OMe)Pd(Y)]. The resultingneutral composition, which will contain the (non-protonated) octadienylligand, is a pi-allyl alkyl complex. The same two ligands (octadienyland protonated octadienyl) can result where 3-methoxy-1,7-octadiene isselected as the methoxyoctadiene compound to start. Where amethoxyoctadiene compound of either type is selected, but the complex isstill in its intermediate form, the resulting composition will includethe specific methoxyoctadiene ligand per se, and will be characterizedas simply a diene complex. While not wishing to be bound by any theory,it is suggested that the various embodiments of the present inventionmay include those where one, or two, or all three Y ligands may bepresent simultaneously in the solution, each as a ligand in its owncomplex with palladium and the given oxaphosphaadamantane ligand. Eachof these embodiments is separately or in any combination thereof usefulas a catalyst composition of the present invention, provided, aspreviously discussed, that the requisite Pd to TMPTA-di-OMe equivalentsratio is applied during the formation thereof.

Successful preparation of the inventive catalyst compositions may beconfirmed via analysis of the compositions using any of a variety ofstandard analytical techniques. Particularly useful and convenient maybe well-known techniques such as nuclear magnetic resonance (NMR)spectroscopy, electrospray ionization mass spectrometry (ESI-MS), andcombinations thereof. Those skilled in the art will be well aware ofmethods whereby these instruments may be successfully applied in theidentification process.

A particular advantage of the present invention is that the compositionsthereof may, in certain particular embodiments wherein the complex is insolution, exhibit surprisingly enhanced solubility and storage stabilityunder most conventional storage conditions. Such conditions may includetemperatures ranging from about 0° C. to about 100° C., preferably fromabout 5° C. to about 60° C., and pressures ranging from about 0 poundsper square inch gauge (psig, approximately 0 kPa) to about 30 psig(approximately 206.8 kPa). The enhanced solubility and storage stabilityare both unexpected because, as is well-known to those skilled in theart, Pd(II) complexes are reduced slowly, but predictably, under suchconditions to form neutral Pd(0) complexes, such as Pd(PPh₃)₃ orPd(TCMPP)₂(CH₂═C{(C═O)Me}₂. These resulting Pd(0) complexes aretypically substantially less soluble in a primary aliphatic alcohol,such as methanol, than are, for example, Pd(II) complexes and, whetherused as the initial palladium source or formed as the result ofprogressive reduction, can precipitate on process equipment surfaceswith which they come into contact. Such precipitation may lead toplugging and, therefore, to interruption of processes, such as butadienetelomerization, in which the compositions are used for catalysispurposes. Without wishing to be bound by any theory, it is suggestedthat the inclusion of the methoxyoctadiene compound in the inventiveprocess, and therefore of any of its ligand forms, as discussedhereinabove, in the inventive compositions, particularly where theprocess is carried out using the stated preferred ratio of equivalentsranges, imparts a degree of resistance to formation of such insolublecomplexes from Pd(II) materials, and/or actually oxidizes Pd(0)materials to convert them back to more soluble Pd(II) materials. Theresult is, then, improved process operability and reliability when thecompositions are to be stored and/or used in, for example, atelomerization reaction.

For purposes hereof, the combination of the palladium metal (which,during the compositions' formation, arises from the palladium source)and the1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantaneligand in the primary aliphatic alcohol forms a solution. This solutionmay be generally termed a “catalyst precursor,” while addition of themethoxyoctadiene compound thereafter, to form a methoxydiene,octadienyl, or protonated octadienyl ligand in further complextherewith, but without reference to order of addition or of resultingcomplexation, may be generally understood as serving to convert the“catalyst precursor” to form a “catalyst.” Such “catalyst composition”may alternatively be termed a “catalyst solution,” since it may beformed via dissolution of its requisite palladium source and sources ofthe oxaphosphaadamantane ligand and one of themethoxyoctadiene-generated ligands in the primary aliphatic alcohol. Itis frequently most convenient to use the catalyst in this form, i.e., asa solution, without further processing. However, it will be understoodthat the complex can, following its initial formation in solution in theinventive process, be separated from any solvent such that it forms aparticulate solid that is typically off-white in color. This particulatesolid will, upon analysis (by 1H or 31P nuclear magnetic resonance (NMR)spectroscopy or electrospray-ionization mass spectrometry (ESI-MS)), beshown to exhibit the expected 1:1 stoichiometry of palladium to eachligand. Furthermore, when redissolved in a primary aliphatic alcohol,the resulting catalyst solution will exhibit the invention's improvementin solubility and storage stability, provided that a slight excess ofthe TMPTA-di-OMe ligand (from greater than 0.1 to 0.3 equivalents, i.e.,such that the complex can be re-formed from an equivalents ratio ofpalladium to TMPTA-di-OMe ranging from greater than 1:1.1 to 1:1.3) isalso included in the solution.

The compositions and processes of this invention have particular utilityin that they are, and/or result in, a catalyst that requires little, orpreferably essentially no, induction time before entering into thereaction wherein butadiene may be telomerized. Such telomerizationoccurs as a result of formation of a reaction fluid, i.e., from contactbetween the catalyst composition of the invention and butadiene,typically 1,3-butadiene, and desirably forms a methoxyoctadienecompound. “Reaction fluid” will therefore be understood to include thebutadiene, diluents (if any, typically methanol), and the catalyst(which may itself be in solution form in a primary aliphatic alcohol),but may further include, either as part of the catalyst solution oradded to the reaction fluid separately, a carboxylic acid and/orpromoter.

The telomerization reaction itself is advantageously conducted in asealed reactor at a pressure at least equal to the sum of vaporpressures of the reaction fluid components, and preferred reactiontemperatures preferably range from 25° C. to 120° C. The pressure may beincreased above the sum of the vapor pressures by pressurizing an inertgas, such as nitrogen, into the reactor, and is preferably greater than0.1 megapascal (MPa) (approximately 15 pounds per square inch, psi), andstill more preferably greater than 0.4 MPa (approximately 58 psi), topreferably less than 4 MPa (approximately 584 psi), more preferably lessthan 3 MPa (approximately 438 psi), and still more preferably less than2 MPa (approximately 292 psi).

The following examples are intended to be illustrative of the presentinvention and are not intended to be, nor should they be construed asbeing, limitative of its scope in any way. Comparative examples are alsoprovided to enhance the reader's understanding of certain aspects of thepresent invention.

Example 1

1:1 Equivalents Ratio, Pd to TMTPA-di-OMe.

In the glovebox, dissolve 94 milliliters (mL) methanol (MeOH), 29 mL1-methoxy-2,7-octadiene (MOD-1), and 91 microliters (μL) acetic acid(AcOH) to prepare a stock solution that is 25 weight percent (wt %)MOD-1 and 75 wt % methanol.

Dissolve palladium(II) acetylacetonate (Pd(acac)₂) (0.0196 grams (g),0.000064 moles (mol)),1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane(TMTPA-di-OMe) (0.0227 g, 0.000064 mol), and 5 mL of the stock solutionthat is 25 wt % in MOD-1 described above to form an inventive catalystsolution. Allow the catalyst to stir for 3 days at 20° C. before use.

Add dibutyl ether (Bu₂O, 5 mL) (GC standard), MeOH (13.35 mL),methylcyclohexane (MeCy, 1 mL) (a liquid fill that approximatesconditions in a plant reactor), the catalyst (0.15 mL), and a portion ofa solution of sodium methoxide (NaOMe) in MeOH (19.32 millimolar (mM),0.5 mL) to a Fisher-Porter bottle. Seal the bottle with a valve equippedwith a septum port. Distill butadiene (approximately 5 mL) into agas-tight syringe, and determine the mass of butadiene by weighing thesyringe before and after addition to the reactor. Inject the butadieneinto the Fisher-Porter bottle with the needle placed below the surfaceof the solution. Place the reaction vessels into preheated oil baths.Remove 1 mL reaction aliquots at the 30 minute (min), 1 hour (h), 2 h,and 4 h time points through a 24 inch (24″) needle equipped with agas-tight valve, and subject each aliquot to gas chromatographic (GC)analysis.

Perform GC analyses on an AGILENT™ 7890 A chromatograph (AGILENT is atrademark of Agilent Technologies) using a DB-1701 column at constantgas flow. Use dibutyl ether as the internal standard, and determineresponse factors based on materials of known composition.

GC Method:

Column: LTM-DB-1701; Length: 30 meters (m); Diameter: 320 micrometers(μm); Film thickness: 1.0 μL; Mode: constant flow; Initial column flow:1.27 milliliters per minute (mL/min).

Front inlet: Mode: split; Initial temp: 250° C.; Pressure: 6.7 poundsper square inch (psi); Split ratio: 50:1.

Detector: FID; Temp: 260° C.; H₂ flow: 40 mL/min; Air flow: 400 mL/min;Make-up gas: He.

Oven: 250° C.

Low thermal mass (LTM) column: Initial temp: 50° C. and hold for 2 min;Ramp at 7.5° C./min. Total run time: 22 min.

Observe no solids precipitation of the catalyst composition afterstoring for more than 4 weeks.

Example 2

After 2 weeks of storage of the catalyst composition of Example 1,conduct a telomerization reaction of butadiene using it, in duplicate,at 70° C. Conversion versus time is shown in Table 1.

TABLE 1 Telomerization reaction run in duplicate at 70° C.Pd:TMTPA-di-OMe = 1:1. Time Conversion of Selectivity MOD-1 Yield MOD-1(min) butadiene (%) (%) (%) 30 49.2/54.8 94.3/94.0 46.4/51.5 6068.0/72.5 94.6/94.4 64.3/68.4 120 84.6/86.0 94.8/94.6 80.2/81.4 24091.8/90.0 94.8/94.5 87.0/85.0

Example 3

1:1.2 Equivalents Ratio, Pd to TMTPA-di-OMe.

Prepare the catalyst as in Example 1, but with 0.0273 g (0.000073 mol)TMTPA-di-OMe. Observe that the catalyst shows no solids precipitationafter storing for more than 4 weeks.

Example 4

After the 4 weeks catalyst storage, use the catalyst composition ofExample 3 to conduct a telomerization reaction at 70° C. Conversionversus time is shown in Table 2.

TABLE 2 Telomerization reaction run in duplicate at 70° C.Pd:TMTPA-di-OMe = 1:1.2. Time Conversion of Selectivity MOD-1 YieldMOD-1 (min) butadiene (%) (%) (%) 30 62.6/55.6 93.5/94.0 58.5/52.3 6072.1/66.0 93.7/94.1 67.6/62.1 120 83.6/79.2 93.8/94.2 78.4/74.6 24087.7/83.2 93.9/94.2 82.4/78.4

Example 5

1:1.3 Equivalents Ratio, Pd to TMTPA-di-OMe.

Prepare another catalyst by dissolving Pd(acac)₂ (0.3200 g, 0.0011 mol),TMTPA-di-OMe (0.5000 g, 0.0014 mol), 70% acetic acid in water (0.6400 g,0.0011 mol), MOD-1 (9.1100 g, 0.0650 mol) in MeOH (27.34 g, 34.5 mL).Stir this catalyst for more than 3 days. Dissolve 0.75 g of NaOMe in 300mL MeOH to make a stock solution of NaOMe promoter. Conduct atelomerization reaction in a Parr reactor at 80° C. with 345 mL of MeOH,198 g of crude C4 (49.4 wt % butadiene, with the remainder beingprimarily butanes and butenes), 8.4 mL of the NaOMe stock solution, 15.6mL of heptane, 12.6 mL of a solution of diethylhydroxamic acid (DEHA) inMeOH (0.021 M), and 2.1 mL of the catalyst. Observe that the catalystshows no solids precipitation after storing for more than 4 weeks.

Example 6

Use the catalyst composition of Example 5 in a butadiene telomerizationat 80° C.

Conversion of butadiene versus time is shown below in Table 3.

TABLE 3 Telomerization in a Parr reactor at 80° C. Pd:TMTPA-di-OMe =1:1.3. Time Conversion of Selectivity MOD-1 Yield MOD-1 (min) butadiene(%) (%) (%) 5 36.1 90.9 32.8 30 62.3 92.4 57.6 60 82.0 92.3 75.7 90 90.192.5 83.3 120 93.4 92.5 86.4 150 95.2 92.5 88.1

Example 7

1:1.2 Equivalents Ratio, Pd to TMTPA-di-OMe.

Prepare the catalyst as in Example 1, but with 0.0768 g (0.00020 mol)TMTPA-di-OMe, 0.0510 g Pd(acac)₂ (0.00017 mol), 9.1 μL acetic acid(0.00017 mol), 2.148 g 1-methoxy-2,7-octadiene, and 6.315 g methanol.Observe that the catalyst shows no solids precipitation after storingfor more than 4 weeks at 40° C.

Example 8

Use the catalyst of Example 7 for a telomerization reaction at 60° C.Conversion versus time is shown in Table 4.

TABLE 4 Telomerization reaction run in duplicate at 60° C.Pd:TMTPA-di-OMe = 1:1.2. Time Conversion of Selectivity MOD-1 YieldMOD-1 (min) butadiene (%) (%) (%) 30 45.7/37.6 96.0/95.7 43.9/36.0 6057.1/58.0 95.5/95.6 54.5/55.4 120 69.5/74.6 95.4/95.4 66.3/71.2 24080.7/84.0 95.3/95.3 76.9/80.1

Comparative Example A

1:1.4 Equivalents Ratio, Pd to TMTPA-di-OMe.

Prepare the catalyst as in Example 1, but with 0.0307 g (0.000086 mol)TMTPA-di-OMe. After 1 week of catalyst storage, observe theprecipitation of a white solid, showing that this equivalents ratioproduces an unstable product.

Comparative Example B

1:2 Equivalents Ratio, Pd to TMTPA-OMe.

Prepare a comparative catalyst using a different but similaroxaphosphaadamantane for the catalyst, i.e.,1,3,5,7-tetramethyl-6-(2-methoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane(TMTPA-OMe), instead of the 1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane(TMTPA-di-OMe) which is used to form the inventive catalyst. TheTMTPA-OMe ligand may be represented schematically as structure (VI):

To accomplish this, dissolve Pd(acac)₂ (0.7100 g, 0.0024 mol), TMTPA-OMe(1.5000 g, 0.0047 mol), 70% acetic acid in water (0.1410 g, 0.0024 mol),and MOD-1 (19.990 g, 0.1426 mol) in MeOH (60.000 g, 76.00 mL). Stir thiscatalyst solution for more than 3 days. Observe the precipitation of awhite solid.

Comparative Example C

1:1 Equivalents Ratio, Pd to TMTPA-OMe.

Prepare another comparative catalyst by dissolving Pd(acac)₂ (0.7100 g,0.0024 mol), TMTPA-OMe (0.7500 g, 0.0024 mol), 70% acetic acid in water(0.1410 g, 0.0024 mol), and MOD-1 (19.990 g, 0.1426 mol) in MeOH (60.000g, 76.00 mL). Stir this catalyst for more than 3 days. Observe theprecipitation of a black solid.

Comparative Example D

1:1.4 Equivalents Ratio, Pd to TMTPA-OMe.

In a glovebox, dissolve 94 mL methanol (MeOH), 29 mL1-methoxy-2,7-octadiene (MOD-1), and 91 μL acetic acid (AcOH) to preparea stock solution that is 25 wt % MOD-1 and 75 wt % methanol.

Dissolve palladium(II) acetylacetonate (Pd(acac)₂) (0.0196 g, 0.000064mol),1,3,5,7-tetramethyl-6-(2-methoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane(TMTPA-OMe) (0.0291 g, 0.000090 mol) and 5 mL of the stock solution thatis 25 wt % in MOD-1, as described in Comparative Example C, to form acatalyst. Allow the catalyst to stir for 3 days at 20° C. Observe theprecipitation of black solids.

Comparative Example E

1:1.8 Equivalents Ratio, Pd to TMPTA-OMe.

Repeat the pre-catalyst preparation as described in Comparative ExampleD, but increase the amount of TMPTA-OMe (0.0374 g, 0.000118 mol).Observe the precipitation of white solids.

The above examples and comparative examples illustrate the improvedstorage stability of the inventive compositions in comparison withcompositions comprising a complex having either a different but similarligand (a1,3,5,7-tetramethyl-6-(2-methoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane(TMTPA-OMe) ligand instead of a1,3,5,7-tetramethyl-6-(2,4-di-methoxphenyl)-2,4,8-trioxa-6-phosphaadamantane(TMTPA-di-OMe) ligand, which differ from one another only in thepresence or absence of a single methoxy group on the phenyl group), orin comparison with compositions comprising the same ligand but at a Pdto TMTPA-di-OMe equivalents ratio that is outside of the greater than1:1 to 1:1.3 range that produces a storage-stable and more solubleproduct. In each of these comparisons, visibly discernible precipitateis encountered in the comparative's performance, either immediately orupon standing for a relatively short period of time, as specified, andtherefore telomerization is not attempted therewith. In sharp contrast,telomerizations carried out using the inventive catalyst compositionsare very successful.

The invention claimed is:
 1. A catalyst composition useful forcatalyzing the telomerization of butadiene comprising a complexcomprising palladium, a 1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane ligand, and a ligand selected from amethoxyoctadiene ligand, an octadienyl ligand, and a protonatedoctadienyl ligand.
 2. The composition of claim 1 wherein themethoxyoctadiene ligand is selected from 1-methoxy-2,7-octadiene and3-methoxy-1,7-octadiene.
 3. The composition of claim 1 wherein thecomplex is dissolved in a primary aliphatic alcohol.
 4. The compositionof claim 3 wherein the primary aliphatic alcohol is selected frommethanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol,glycerol, and combinations thereof.
 5. The composition of claim 1wherein the composition further comprises at least one of: (a) thecounteranion of a carboxylic acid; (2) a promoter selected fromalkoxides, enolates, phenoxides, borohydrides, and hydrazides, all ofalkali metals; alkaline earth metals and quaternary ammoniums; alkalimetal salts; and combinations thereof; and (3) combinations thereof. 6.The composition of claim 1 wherein the ratio of equivalents of thepalladium to equivalents of the1,3,5,7-tetramethyl-6-(2,4-dimethoxyphenyl)-2,4,8-trioxa-6-phosphaadamantane ligand is from 1:1.1 to 1:1.3.